Recently I was under my kitchen sink and discovered a pool of water under it. Upon further investigation I noticed a moderate drip on the cold-water valve. What was odd (to me, at least) was that turning the valve on or off had no effect on the drip rate. I then discovered that the drip was actually on the line-side of the valve (As seen in the second picture). It looks like it drips where the line connects and then dribbles off the bottom.
I have never done any plumbing beyond changing a shower head. Is this something I can fix with my limited skills, or should I call a plumber? I have never shut off water to my house before and am afraid I will mess something up horribly. If I can fix it, what do I do exactly?